This invention relates to bulldozer attachments for tracked vehicles and more particularly to the coupling of a bulldozer blade to a crawler vehicle of the form which rides on four track assemblies each of which is capable of a degree of vertical and lateral oscillation relative to the vehicle body.
Crawler tractors and most other forms of tracked vehicle are usually provided with a pair of track assemblies each of which extends along an opposite side of the vehicle. In the conventional construction the two track assemblies may have a limited degree of freedom to oscillate or pivot vertically relative to the vehicle body to accommodate to terrain irregularities and are usually constrained against outward and inward oscillation. Most prior mounting structures for supporting a bulldozer blade at the front of such a vehicle have a pair of push arms each of which extends backward from an opposite side of the blade to connect with the track frame of a separate one of the track assemblies, usually through trunnion bearings or other forms of universal joint. Additional bracing is often provided between the back of the blade and the push arms or between the back of the blade and the vehicle body to increase resistance to loads and to provide for one or more of several forms of positional adjustment of the blade such as lifting and lowering, tipping, tilting and angling. In many instances such bracing is formed in part of extensible and contractable fluid cylinders in order to facilitate changes of blade position during operation.
The known forms of bulldozer attachment are not adaptable to certain specialized forms of crawler vehicle in which the track frames may have greater freedom of movement than is the case with the conventional two-tracked crawler vehicle. One highly advantageous form of crawler vehicle is supported on four spaced-apart essentially parallel crawler track assemblies which extend lengthwise beneath the vehicle body. Ground pressure is reduced and traction, flotation and stability are enhanced by a suspension system which allows the forward portion of each track assembly to rise and fall independently of the others to accommodate to irregular terrain. The suspension system also enables the outer and inner track assemblies below the right portion of the vehicle body to oscillate outward and inward as a unit while enabling the two track assemblies below the left side of the vehicle to oscillate outwardly and inwardly as a unit in a similar but independent manner.
Because of this novel freedom of motion of the track assemblies relative to each other and to the vehicle body, bulldozer attachment push arms cannot simply be coupled to the outermost track frames in the conventional manner without creating operational problems. Depending on the specific bulldozer attachment construction, this conventional mode of coupling may variously interfere with the oscillations of the track assemblies, or cause severe stresses and loading at certain portions of the bulldozer attachment or cause the blade to undergo undesirable positional changes as the track assemblies oscillate vertically and laterally in response to terrain irregularities.